1. Field of the Invention
The invention is directed to a method for calibrating a network analyzer.
2. Description of the Prior Art
A method of the specified type is known (U.S. Pat. No. 4,982,164). Here, it is preferred to use as the two-port unit a direct connection of the two test ports (Through Testing) where four calibration measurements are performed. Subsequently, at least three further calibration measurements are performed on two further calibration standards; for example a one-port unit R of known reflection (Reflect Testing) is used as the second calibration standard which is successively linked to the two test ports, and preferably a matched load M (Matched Load) is used therefor. A one-port unit of random reflection which is, however, different from the reflection of the second calibration standard, is used as the third calibration standard, for example a short circuit S (Short Circuit) or an open circuit (Open Circuit) that is linked to only one of the two test ports. As compared with the commonly used 12-term calibration method ("Neues von Rohde & Schwarz" 108, winter of 1984/85, pp. 26 and 27) this known calibration method is simpler because, in addition to the calibration two-port unit of which all complex scattering parameters are known (e.g. two-port T), only three further calibration standards are required (e.g. M1, M2, S1); however, this method does not eliminate a drawback of the commonly used 12-term method which resides in that both of the test ports must be accessible for these additional tests on calibration one-port units, because one of the one-ports, for instance the matched load M, must still be linked to the two test ports.